Coded track circuit signaling system for railroads



T. J. JUDGE 2,635,180

2 SHEETS-SHEET 1 Snventor CODED TRACK CIRCUIT SIGNALING] SYSTEM FOR-RAILROADS A ril 14, 1953 Filed May 22, 1947 @Gttomeg April 14, 1953 T. J. JUD E:

CODED TRACK CIRCUIT SIGNALING SYSTEM FOR RAILROADS Filed May 22, 1947 2 SHEETS-SHEET 2 JOIFZOO 3nnentom Patented Apr. 14,, 1953 CODED TRACK CIRCUIT SIGNALING SYSTEM FOR RAILROADS Thomas J. Judge, Rochester, N. Y., assignor to General Railway Signal Company, Rochester,

Application May 22, 1947, Serial No. 749,742

11 Claims.

This invention relates to coded track circuit signaling systems for railroads, and it more particularly pertains to the conservation of energy in coded track circuits.

It is well known that a higher degree of track circuit energization is required to obtain satisfactory operation of a code following track relay at a fast code rate than at a slow code rate, assuming the same percentage of on and off time for each code rate. This is true because of the inductive windings of the track relays requiring time for current to build up, and for a short pulse which does not allow time for full build up of the current it is necessary to use a higher energizing potential in order that the current may build up for each pulse to the operating value of the relay. Thus it is the usual practice to adjust the potential applied to the track circuit to obtain satisfactory operation at the highest code rate employed. Such arrangement obviously provides a higher drain on the source of track circuit energy than is required for the lower code rate, and thus track circuit power, which is often necessarily furnished by primary batteries, is wasted.

An object of the present invention is to reduce the power consumption in a coded track circuit, :and yet maintain the same degree of dependable operation, by applying a lower potential to the track rails for the transmission of pulses at a lower code rate than is applied for the transmission of pulses at a higher code rate.

Another object of the present invention is to increase the resistance in series with the source of energy connected to the track rails in response 'to the presence of a train in the associated track section.

Another object of the present invention is to reduce the code rate in a track section in response to the presence of a train in that track from the accompanying drawings, and in part pointed out as'the description progresses;

In describing the invention indetail, reference is made to theaccornpanying drawings-in which like letter reference charactersaref generally used to designate similar parts which are made .dis-

tinctive by reason of preceding numerals characteristic of the particular location or signal with which such parts are associated, and in. which:

Fig. 1 illustrates one embodiment of the present invention as applied to specific typical track sections of a stretch of railway track; and,

Fig. 2 illustrates another embodiment of the present invention as applied to certain typical track sections of a stretch of railway track.

For the purpose of more clearly illustrating the mode of operation of the system provided by the present invention, rather than illustrating the specific structure and arrangement of parts that would be employed in practice, the respec tive embodiments of Figs. 1 and 2 of the drawings have been illustrated by schematic wiring diagrams of a conventional nature. The symbols and in the diagrams are used to indicate connection to the respective positive and negative terminals of a suitable direct current source of energy.

With reference to Fig. 1, a stretch of railway track is illustrated as being divided into respective track sections IT, 2T, 3T and 4T in a manner commonly employed in railway signaling practice, and the signals 2, 3, and 4are provided for governing entrance to the respective track sections 2T, 3T, and 4T for governing eastbound traffic (to the right).

The signals illustrated are of the color light type having respective green, yellow, and red color lamp units for indicating proceed, proceed with caution, and danger respectively. It is to i be understood, and it will be readily apparent as able type for generating code pulses at respective and '75 code rates, each pulse being of a length substantially equal to the time spaces between pulses. A suitable oscillator of this character is disclosed in the patent to O. C. Field.

Patent No. 2,351,588, dated June 20, 1944.

The code receiving apparatus at the entrance end of the respective track sections comprises a track relay TR connected across the track rails, and conventional code responsive relays H and D which are of a character to be maintained steadily picked up in response to the pulsing of the associated track relays TR. The relays D respond only to the pulsing of their associated track relays TR at a 180 code rate and when approach control has become effective.

The signaling system according to Fig. 1 is assumed to be such that the signals are normally conditioned to be clear (subject to approach control) when the trackway is unoccupied by trains. Under such conditions, the code transmitter oscillators 5891GT for the respective track sections are normally active to apply code pulses to the track rails at the respective exit ends of the track sections at a l8!) rate and the oscillators 150T are inactive. For example, the oscillator ISiICT associated with the eXit end of the track section ET is normally active in accordance with the energization of a circuit extending from including front contact 20 of relay 3H, back contact 2! of relay ZARP, and winding of 'relay NOT, to I In accordance with the code oscillator -l80CT being normally active, code pulses at a 180 rate are applied across the track rails at the exit end of each of the track sections as is specifically shown, for example, for the application of code pulses to the track rails at the right hand end of the track section ET. The relay ZTR at the left hand end of the track section'ZT is energized for each pulse of the oscillator lSEiCT by a circuit extending from the positive terminal of the battery 22 including the variable resistor RL'front contact 23 of oscillator l8llCT, back contact 24 of relay ZARP, front contact 25 of relay 3H, upper rail of track section 2T, windin of relay 2TB, track resistor R2 and lowerrail of track section 2T, to the negative terminal of the battery 22. A consideration of the circuit which has been described shows that the voltage'applied across the track rails by the code transmitter is limited by the variable resistor RI, whichresistor is adjusted in practice to provide the required amount of operating current for the track relay ZTR at the I86 rate. 7

It is well known in coded track circuit organizations that diiiiculties are encountered at times in coded track circuit operation because of a potential set up in the ballast between the track rails which is not-immediately dissipated upon the termination of each code pulse; It is therefore desirable according to the present invention, although not necessarily required for the operation of some features of the present invention, that a shunt be applied across the track rails by the track circuit code transmitter during the off period between code pulses to accelerate the dissipation of a potential build up between the 4 7 front contact 23 for initiating the application of another code pulse across the track rails. The use of the shunt as has been described during the off periods of the cod-e provides for satisfactory operation of the track relay 2TB, at a minimum voltage applied across the track rails by the code transmitter IBQCT at the right hand end of the track section ET.

The track relays TR, are preferably of the biased polar type adapted to pulse their con tacts in response to code pulses received through the track rails, and when the track rails of the associated track sections are shunted as by the Y 7 presence of trains, the back contacts of the re lays TR are steadily closed.

The pulsing of the contact Z'i of relay ZTR in accordance with the 180 code received at the left hand endof the track section 2T provides for the clearing of signal 2 as indicated by the dotted line 28 in a manner corresponding to that which is specifically illustrated for the clearing of signal'3 in accordance with the pulsing of the track relay3TR.

The pulsing of contacts 29 and 39 of relay STR. is effective to energize the direct current relay 3H through the decoding transformer 3! and the rectifying contact 36 in a manner well known to those skilled in the art. With the relay 3H picked up,'the closure of front contact 32 conditions a circuit for the relay 3!) by which such relay can be energized'when approach control for the signal 3 is" rendered effective. The closure of front contact'33 of relay 3H in'the control circuit for the lamps of signal 3 conditions' a circuit for the energizing of the'green or yellow lamp of such signal, as selected by the relay 3D, but the lamps are normally dark because of the front contact 313 of relay 2ARP being open.

Having thus considered the conditions of the system which can be assumed to be the normal rails by the track ballast. Itis therefore provided, subsequent to theopening of the track circuit at front contact 23 at the termination of each of the code pulses generated by the code transmitter relay I8BCT, that a shunt is closed across ,the track rails upon the closure of back contact 26 of the oscillator itGCT during each off period of the code being transmitted. Such shunt in the track section2T can be traced as extending from the upper rail of the track section 2T including front contact 25 of relay 3H, back contact 24 of relay EARP, and back contact 26 of oscillator i 89 CT to the lower rail ofthe track sec-. tion 2T. Such shunt is obviously'removed when the oscillator l 800T shifts its contacts t 105 3 11.15

conditions, when the trackway is unoccupied by trains, consideration will now be given to the mode of operation of the signaling system under certain typical trafiic conditions.

It will thus be assumed that an eastbound train accepts the signal 2 and enters the track section 2T. The presence of the train in track section 2T, by shunting. the track rails of that track section, causes increased current fiow through the series resistor PM Which is included in the track'circuit which has been described,

and the increased voltage dropacross this resistor is effective to cause the relay 2ARto becomeactive. The relay ZAR is connected in multiple with the resistor RI by a circuit extending from the right hand terminal of the resistor R5 and including resistor R4 and back contact 35 of relay ZARP, front contact 36 of relay 3H and winding of relay ZAR, to the left hand terminal of the resistor RI.

The structure of the relay 2AR is preferably of the general character of the code following track relays TR so as to follow the code as applied to the track rails of the track section 2T when that track section is shunted. The pulsing of the contact 31 of relay ZAR causes the relays EARS and 2ARP to become successfully picked up. When the relay ZARS is picked up by the pulsing of contact 31 of relay ZAR, it is maintained 1 steadily energized by its stick circuit for a time interval required to effect the picking up of relay ZARP, which is preferably made to have slow pick 2ARP, front contact 38 of relay 2ARS, and windbeing received at the left hand end of the track section 3T. More specifically, a circuit is closed for the upper portion for the primary winding of the decoding transformer upon the closure of front contact 29 of relay 3TB. Such circuit extends from including front contact 29 of relay 3TB, front contact ii! of relay EARS; and

upper portion of the primarywinding of transformer 39, to The dropping of the relay 3TB at the end of each pulse opens the circuit which has been described at front contact 29 and closes a circuit at back contact 29 for the lower portion of the primary winding of the transformer 39. Such circuit extends from includingback contact 29 of relay 3TR, front contact 32 of relay 3H, front contact 4! to relay ZARS, and lower portion of the primary winding of the transformer 39, to

The output of the decoding transformer 39 is coupled to the input terminals of the tuned circuit and rectifier unit I8ElDU, such unit being of the character generally employed for similar purposes in coded track circuits. The direct current relay 3D is connected to the output terminals of the tuned circuit and rectifier unit lElElDU so as to'render that relay picked up only in response to a 180 code received at the left hand end of the track section 3T. pointed out that the relay 3D is normally deenergized, even though there may be a 180 code in the track section 3T, because of such relay approach controlled by the relay ZARS. Thus, relay 3D, and the decoding transformer 3d as well, receives energy only when the track section 2T is occupied by a train which has advanced sufficiently in approach of the signal 3 as to render the approach relay ZAR active.

t It will be seen by the sequence of operation of the relays ZARS and 2ARP, together with the slow pick-up characteristics of 2ARP, thatsuflicienttime is allowed for the picking up of relay 3D in response to the picking up of relay2ARS before the signal circuit is closed by front contact 34 of relay ZARP. This prevents a possible flash of the yellow lamp Y of signal'3 if the relay 2ARP were to become picked up prior to the picking up of the relay 3D. The use of the stick circuit for the relay ZARS to maintain that relay steadily picked up immediately subsequent to its initial energization provides in a positive manner that the continuity of the circuit for-[the primary winding of the transformer 39 is maintained to insure a quick response of the relay 3D.

' The closure of front contact 42 of relay ZARS upon the picking up of thatrelay applies energy to the winding of relay ZARP in an obvious Upon the picking up of the relay ZARP; with the relays 3H and 3D already picked up, the

It has already been r greenllampG of signal 3 becomes energizedbya circuitextending from including front contact 34 of relay 2ARP, front contact 33 of relay 3H, front contact 43 of relay. 3D and the lamp G, to It is thus provided that the approaching controlof the signal 3 is effective upon the approach of a train Within the track section 2T to apply energy to the signal and thus provide a signal indication governin passage of the train into the nextblock.

The picking up of relay ZARP also has another function in that it shifts the code rate applied to the track rails of the track section 2T from a 180 rate to a 75 rate, and in doing so reduces the power drain on the track battery 22 because of theresistor R3 associatedwith the 75y00d6 rate transmission being of a higher value than the resistor RI associated with the 180 code rate transmission. It is also provided that the code transmitter "300T is rendered inactive upon the picking up of relay 2ARP by the opening of back contact 2 Land the codetransmitter 15CT is rendered active in accordance with the closing of a circuit extending from including front contact of relay 3H,'front contact 2! of relay ZARP, and winding of oscillator 'IECT, to

The pickin up of relay ZARP is eifective to open the branch of the track circuit including the 180 code oscillator contacts 23 and at at back contact 24, and the closure of front contact 24 of relay ZARP renders the transmission of code pulses effective at a '75 rate. Thus a reduced potential is applied across the track rails at the right hand end of the track section :ZT. The circuit by which such pulses are applied extends from the positive terminal of the track battery 22 including the adjustable resistor R3, front contact 44 of the oscillator 150T, front contact 24 of the approach control relay ZARP, front contact of relay 3H, upper rail of track section 2T, Winding of relay ZTR, track resistor R2, and lower rail of track section 2T; to the negative terminal of the track battery 22. It is thus provided that the power consumed in the track circuit for the track section 2T is reduced because ofthe presence. of the train in the track section uponthe shifting of the code rate from a 180 to a ra te because of the selective inclusion of a higher resistancefor the 75 code rate than for the lcode rate.

Duringthe off periods of the code, the closure of back contact 450i oscillator T shunts the track rails as has been described with respect to the shunting of the track rails by back contact ofoscillator I8BCT. y Y

Inasmuch as the approach control relay EAR is energized principally by the voltage drop across the track resistor, the control circuit of such relay must be selectively controlled so as to shift the control of that relay from one track resistor to the other as the code rate in the track section is changed. Thus it is provided that the picking up of the relay ZARP as l-has been heretofore described not only shifts. the code rate applied to the tracksection' 2T, but also shifts the connection of theapproa ch controlrelay ZAR so that such relay, rather than being energized by the voltage'drop across the resistor BI, is energized by the voltage dropacros the resistor R3. This shifting-of the'controlcircuit for the relay ZAR isfaccomplished uponthe shifting of contact 35 to" select between the resistor R1 and R3 in an obvious manner, the resistor R5 being included inthe circuit rather thanthe resistor R5 of r elatively lower resistance. This maintains lsubstanstrain shifting from the voltage drop across RI to'the voltage dropacross R3. V

Upon the shiftingjof the code rate from a 180 code to a75 code, the current in the track circuit is reduced in a manner which has been heretofore described, andthus the current is less through the resistor R3 than formerly existed through the resistor RI. The resistance R3 being greater thanRI provides that the potential drop across the resistor R3 for the operation of the approach control relay ZARis of a value relatively close to the potential drop across resistor RI by which the relay 2AR is assumed to have been initially rendered active. Because of the reduction of current in the remainder of the track circuit, the potential drop across such remainder of the circuit decreases, and thus the drop across R3 must be'greater to some extent than the prior drop across RI. This is desirable because it provides that once the. approach relay 2AR has been rendered active, it is maintained active at a higher potential rather than being operated at a marginal potential, and thus is more positive in its operation.

Assuming the train to progress farther along the trackway so as to accept the signal 3 and enter the track section 3T, the shunting of the track rails of the track section 3T causes the relay 3H to be dropped away, and the dropping away of that relay, upon the closure of back contact 33, with the relay ZARP still in its picked up position, provides for the energization of the red lamp R of signal 3. The green lamp G of that signal is deenergized upon the shifting of that contact. 1

In accordance with the dropping away of relay 31-1, the code oscillator 150T is maintained active, and the oscillator I80CT is maintained inactive in an obvious manner by the shifting of contact 20.

In the track circuit for the track section 21, the track rails are maintained energized with code pulses at a 75 rate by a circuit extending from the positive terminal of the track battery 22 including the variable resistor R3, front contact 64 of oscillator 150T, back contact 25 of relay 3H, upper rail of track section 2T, winding of the track relay 2'I'R, variable resistor R2, and lower rail of track section 2T, to During the on periods of the code, the track rails are shunted from the upper rail through back contact 25 of relay 3H and back contact 45 of oscillator 150T, to the lower rail of the track section 2T. The closure of back contact 36 of relay 3H maintains the relay 2AR active as long as the train shunt is maintained in the track section 2T.

It will be readily apparent that the code transmitter at the right hand end of the track section 2T is efiective to apply 75 code pulses to the track rails as long as the relay 3H remains in its dropped away position, irrespective of the approach relay 2AR being rendered inactive when the track section 2T becomes unoccupied in the rear of the train. The rendering inactive of relay 2AR under such conditions causes the relay ZARS to be dropped away when the contact 3'! of relay 2AR is rendered inactive, and thus the opening of front contacts 40 and 4| of relay ZARS is efiective todisconnect the relay 3D and its decoding transmitter from the track contact 29 of relay 3TB. The opening of front contact 42 of relay ZARS provides for the dropping away of relay ZARP, and upon the dropping away of that re1ay,--the opening of front contact 34 extinguishes the red lamp R of signal 3 and thus restores that signal to its normally dark. condition.

' Upon further progress of the eastbound train so as to leave the track section 31 unoccu ied in the rear of the train, a 75 code transmitted through the track rails of the track section 3T is effective to cause the picking up of relay 3H to complete the restoration of the track' circuit apparatus for the track section 2T to the conditions which have been described when considering the normal conditions of the coded track circuits when no trains are'present. The picking up of relay 3H under such conditions changes the code rate in track section 21 from a '75 code to a 180 code by the shifting of contacts 20 and 25, and contact 36 shifts the connection to the relay 2AR from resistor R3 to resistor RI, which resistor is associated with the transmission of code pulses at a 180 rate.

With reference to Fig. 2 another embodiment of the present invention is illustrated in which the approach control and reduction in code rate upon the approach of a train is accomplished by the use of inverse code rather than by theuse of series or shunt type approach control relays.

The trackway to which the signaling system is applied comprises respective'track sections IIT, IZT, I3T and MT, and signals l2, I3, and I4 are provided for governing entrance into respective track sections IZT, I3'I', and MT. Signaling is provided for governing the movement of eastbound train (to the right), and the signals can be of any conventional signal structure as has been heretofore pointed out. Code transmitter oscillators T and I8$JCT correspond to oscillators which have been described specifically ith reference to Fig. 1, and inasmuch as an inverse code receiver track relay is required at the exit end of each of the track sections, thetrack relays associated with each track section are designated as relays ATR and BTR provided with suitable prefixes. A relay ATR is at the entrance end of the track section for receiving driven code pulses, and a relay BTR is at the exit end for receiving inverse code pulses. The relays ATR are of the conventional code following biased polar type, while the relays BTR are illustrated as being of the magnetic stick type, particularly for the purpose of improving the operating characteristics of the track circuit with respect to the reception of inverse codes. It is to be understood, however, that other types of code following relays can as well be used in accordance with the requirements of practice.

e To consider first the condition of the apparatus when no trains are present, conveniently calling the normal condition of the system, it will be assumed that there are no trains present in the trackway, and the condition of the relays at that time is as illustrated in Fig. 2 in which it is shown that the oscillator IBQCT is normally active for the transmission of a code in the tracksection HT and the oscillator 150T is normally inactive.-

The track circuit for each code pulse of the oscillator ItilCT is closed from the positive terminal of the track battery 59 including the variable resistor RH], contact 5! of oscillator I 890T in its upper position, back contact 52 of relay I2AP, front contact 53 of relay I3I-I, upper rail of track section. I 2T, winding of relay IZATR, back contact 54 of the inverse code transmitter relay IZRCP, variable resistor R20, lower rail of track section HT, and lower Winding of the inverse code receiver relay IZBTR, to the negative terminal of (not shown) is picked up in a manner corre-j sponding to that specifically illustrated for the The lower winding of the inverse code receiver relay IZBTR is so conenergization of the relay IBH which is asscciated with the control of the signal i3. is illustrated as being energized normally through the pulsing of contacts 56 and 53'01 the code following track relay IEATR. V

At the termination of each i driven code pulse transmitted from the right-hand end ormeaack section l2T, the relay JERCP is picked up for-the transmission of an inverse code-pulse a' manner corresponding to that which is specifically illus: trated for the pickup of therelay IBRCP at the entrance end of the track section l 3T; Thus the relay l3RCP is illustrated as being pickedup upon the termination of a driven code pulsewhen a circuit is closed extending from 4+),"including back contact 560i the code following track relay I3ATR, front contact58 of relay IBHQrectifier 59,

back contact 68 of relay H3RCT, and winding of relay 1% RCP, to At the-same time energy is applied to the winding of the relayifrRCT except thatit is applied-through thevariablereactor 6i, and thus the picking up of the relay lfiRCT is delayeolto provide timing *"for-measuring the duration of the inverse code pulse being transmitted. lt will be readily apparent that the adjustment of thevariable reactor jB-l can readily be effective to govern the pick'up time of the relay I3RCT. The pick up circuit for the relay The relay I3RCT extends from ,'including backcontact 56 of relay I3ATR, front contact Elliot-relay 13H, rectifier 62, variable reactor 6!, and thewinding of relay IBRCT, to When therelay l 3RT is picked up, the opening of back contact "Bil deenergizes the inversecode transmitter relay I3RCP, andcauses that relay to be dropped away.

Such relay in dropping awayconne'cts the track 7 relay -|3ATR across the track rails throughback contact 63 andthe-variable track resistor R to condition relay I3A'IR for the reception of the next driven codepulse transmitted from, the right-hand end of the track -se ctio n3l3T. The

connection of the track relay -l-3ATR across the track rails at the entrance end of the trackfs'e'ction I3T under such conditions allowssuch relay to respond to the next driven-codepulse, and in its picking up, the openingof ba'ck contact 56 opens the circuits which have been described for 1 the energization of relays |3RCTland liiRCP "for the duration of the reception of the driven code pulse. The rectifiers 59 and 62 'in the circuits for relays I3RCP and ISRCTJ are to efiejctively isolate the relays I3RCP and I3RCT from the primary winding of the transformer '64. The resistor 65 provides a desired-slow drop awaycharacteristic for relay I3RCT by shunting its winding and the reactor 6|.

Having thus considered the manner in which the respective inverse code transmitter relays are active, consideration will now be given tofthe; transmission of theinverse codepulses-through the track rails, and the receptionof such, pulses at the exit end of a typicaltrack section;- Thus,

with reference to the track section l2T, thepicking up of the relay I2RCP for the transmission of an inverse code pulse is efiective to open -the track circuit which has beenydescribedwat back contact 54 and apply the potential of the track The application of such energy to the track rails is effective to energize the magnetic stick relay IZBTR with a polarity to cause such relay to actuate its contacts to their upper positions. The circuit by which the relay IZBTR is energized in response to an inverse code pulse extends from thepositive terminal of the track battery 66 including the variable resistor RGO, front contact 61 of relay IZRCP, front contact 54of relay IZRCP, upper railof track section IZT, front contact 53 of relay 13H, back contact 52 of relay l2AP,;contact:6-B of oscillator l8llCT in its lower position, upper winding of relay I2BTR, and lower rail of track section IZT to the negative terminal of thetrack'battery 66. The terminaticn of the inverse code pulse by the dropping away of relay IZRCP reestablishes the connection I2BH having slow drop away characteristics so as to be maintained steadily picked up in response to the pulsing of the code receiver relay IZBTR.

Withrelay 'i ZBH picked up,'connections to the decoding transformer associated with the control of the relay 13D are opened at back contacts 12 and 73 so as to cause that transformer and the relay 'l3D to be normally deenergized. The

relay lZAPis normally deenergized because the dropping away of relay I2BH is required for closing its pick up circuit. It is thus provided that energy consumption aside from that required for the track circuits at a signal location is limited 7 to that requiredfor 'theoperation of the oscillator ISUCT, for the energization of the relays H and BH at that signal location, and for the actuationof the inverse code transmitter relays RCT and 'RCP. H V I p To consider the mode of operationof the system according to the embodiment illustrated in Fig. 2 upon the passage of a train, it will be assumed that aneastbound train enters the track sectitm upon c pnngithe signalli. The

shunting of the track rails of the track section I2T renders the transmission 'of an inverse code ineffective in that track section for the operation 1 of the relay IZBTR. When the contacts fill and] H of relay IZBTR, become inactive because of the i train shunt, the relayv IZBI-I becomes dropped: away, and the dropping away of that relay, upon theclosure of back contacts 12 and :13, connects the decoding transformer -84 to the contact 56 of the track relay I3ATR so as toprbvid for the energization of the relay 13D through the rectifier and tunedcircuit unit I8BDU.

The dropping away of relay IIZBI-i isalso ef-, V fective upon the closure of back contact'li i to en:

ergize the relay IZAP, which preferably hasslow pick up characteristicsisol as to allow time for; the picking up of the relay 1313 prior to the closureof frontcontact 15 of relay IZAP in the signal control circuit.

Upon the closing of front contact-'15 of relay IZAP, with" the relays [3H and 13D picked up,

the green lamp G of signal I3 is energized by a circuit including front contact 15 of relay IZAP,

front contact 16 ofrelay ISI-L-and front contact 11 of relay l3D. The approach of the eastbound train within the-track section IZT has thus become effective to energize the green lamp G of signal l3 for governing passage of the train into the track section l3T.

Upon the picking up of relay IZAP, the oscillator |8llCT (associated with the code transmitter at the exit end of track section IZT) is rendered inactive, and the oscillator 750T is rendered active by the shifting of contact 18 of relay IZAP.

When the oscillator lBiiCT becomes inactive, its contacts and 68 assume their center positions which have been shown dotted in Fig. 2, thus opening all circuits selected by such contacts. The contacts i9 and 83 of the oscillator 550T by becoming active alternately close their front and back contacts to transmit a 75 code through the track rails of the track section IZT. The relay IZBTR has its upper winding connected across the track rails by the back contact 88, but the train shunt of track section IZ'I renders that relay inactive.

The positive terminal 50 of the track battery is connected t the upper rail ofthe track section I2T for'each '75 code pulse in a circuit including the variable resistor R383, contact 79 of oscillator 7501 in its upper position, front contact 52 of relay I2AP,'and front contact 53 of relay 13H to the upper rail of track section iZTQ The negative terminal of the track battery is con nected to the lower rail of the track section IZT for each pulse of the 75 code through the lower winding of the inverse code receiving relay IZBTR. It has been pointed out that energy flowing through the lower winding .of the relay IZBTR is of a polarity to actuate the contacts of that relay to their lower positions, and that the actuation of such contacts to their upper positions can be comprised only by the reception ofinverse code pulses as applied to the upper winding of the relay I2BTR. It is thus provided that the energy consumption of the track section IZT has been reduced in response to the presence of the train by the shifting of the driven code rate in that track section from a 180 to a 75 code, and thus selecting the inclusion of the higher value resistor R39 in series with the track battery 50 as compared to the value of the resistance R20 that is normally included in series with the track battery 50 for the transmission of a 180 code.

As the train progresses so as to accept the signal l3 and enters the track section I3T, the

control relay I 2AP out of the circuit which has been described. The reception of the 75 code pulses at the left hand end of the track section [2T when such track section has become unoccupied in the rear of the train renders the code following track relay I2ATR active at the 75 code rate to pick up its associated relay IZH (not shown) and thus provides for the.energiza tion of the yellow lamp Y of signal l2 in case a following train is approaching so as to provide approach control for the illumination of that lamp. The inverse code transmitter relay IZRCP is rendered active in accordance with the pulsing of the track relay IZATR by the energization of circuits similar to those which have been described with reference to the control of the inverse code transmitter relay I3RCP.

As the train progresses further along the trackway so as to leave the track section I3T unoccupied, the establishment of'a 75 code in that track section is effective to restore the relay shunting of the track rails of that track'se'ction renders the track relay I3ATR inactive and thus 7 causes the dropping away of the relays [3H and [3D. The shifting of contact 76 of the relay |3H is effective to open a circuit for the green lamp G of signal I 3 and close an obvious circuit for the red lamp R of such signal. It is of course desirable that the relay I3H drop away prior to the dropping away of relay I3D to avoid a flash of the yellow lamp Y of signal 13.

Upon the dropping away of relay I 3H, the

circuit by which the oscillator 150T has been active is opened at front contact 8|, but the closure of back contact 8| maintains such oscillator active. Similarlyin the track circuit, the shifting of contact 53 of relay i3H opens the circuit that has been described for the transmission of 75 code pulses and closes a circuit to maintain the transmission of '75 code pulses which shunts front contact 52 of the approach [3H to its normally energized position, and in accordance with the picking up of that relay the shifting of contacts 8i and 53 is effective to restore the conditions which have been described as normal whereby the oscillator 15C'I' is rendered inactive, and the oscillator IBDCT active for the transmission of a 180 track circuit code in the track section IZT. Such restoration is of course eifective only provided no following train has entered the track section |2T. In case a following train has entered the track section I2T, it will be readily understood by those skilled in the art that the mode of operation of the. system becomes effective uponthe' approach of i such following train in a manner corresponding.

to that which has been described when considering specifically the passage of a single train;

To summarize various respective features of the present invention that are efiective tov save energy, with reference to Fig. 1, it has been described that the shifting of the code rate from a 180 to a '75 rate upon the entrance of a train into the associated track sectionis effective. to reduce the potential across the track rails by the selection of a higher track circuit resistance 'in'series with the track battery. It is also provided according to Fig. 1 that the approach con.- trol relay ZAR can be made a relay of relatively high efficiency because such relay is arranged to operate off the voltage drop across the track resistor RI or R3 included in series with the battery, and thus the windings of such relay can be of high resistance with a large number of turns, as compared to the low resistance winding that would be required if such "approach control relay were to be actuatedsolely because, i. of its inclusion directly in series with the, track.

battery and the track rails.

Further energy saving features of the embodie ment according to Fig. 1 are that the oscillators. 750T and lflllCT are selectivelyrendered active in accordance with Whichever oscillator is .re.- I quired to be active. The circuits including-the decoding transformer 39 and its associated tuned circuit IDU and r ilayillare normally de-- ce iver relay I2BTR that is normally active of course consumes a certain amount of'power, as does anyapproach control device that must necessarily be associated with a track circuit. The oscillators l5CT'and IBBCT of Fig. 2 are selectively rendered active as in Fig. 1, and similarly there is no energy consumed by the relay D and its associated decoding transformer except when approach control is rendered effective. The inverse code transmitter relays RCT and RCP are normally active, but their power consumption can be maintained at a very low level as compared to the power saved by the use of a higher resistance in series with the respective track circuits when their associated track sections are occupied by trains.

Having thus described two specific embodiments of the present invention as limited to-specificstre'tches of railway track, it is desired to be understood that these forms have been se-- lectedmore for the purpose of facilitatingthe typical disclosures of the presentinvention than for limiting the scope of the present invention,

and it is to be further understood that various additions, alterations and modifications may be applied to the specific form shown to meet the requirements of practice, without in any manner departing from the spirit or scope of the present invention except as limited by the pending claims.

What I claim is: n

1. In a code transmitter for applying code pulses at selected high and low code rates to the track rails of a track section, a source of energy, circuit means including said source of energy for applying code pulses at a relatively high potential to the track rails at said high code rate, circuitameans including said source of energy for applying code pulses at a relatively low potential to the track rails at said low code rate, and circuit means dependent upon trafiic conditions for selecting the application of higher low code rate pulses to the track rails.

2. In a railway track circuit code transmitter for applying code pulses across the track rails of a track section at-selected high or low code rates, a source of energy, respective highand low rate coding contacts, respective high and low resistance track resistors, circuit means for selectively connecting said source of energy across the track rails through said high rate contact and said low resistance track resistor or through said low rate contact and said relatively high resistance track resistor, whereby a higher potential is applied to the track rails at said high rate than at said low rate. r

3. In a coded track circuit for a railway track section, a track circuit code transmitter at one end of the track section comprising a source of energy, respective high and low rate code oscillators, and circuit means for selectively connecting said source of energy across the track rails of said track section through a contact of said high rate oscillator or a contact of said low rate oscillator, said means being eiiective to apply a higher potential to the track rails through said contact of said high rate oscillator than through said contact of said low rate oscillator.

4. In a coded track circuit of the character described for a railway track section, a code transmitter at oneend of the track section for applying energy pulses to the track rails at a selected code rate comprising, a source of energy, respective high and low rate coding contacts, and circuit means for selectively governing the potential'applied tothe track rails "from said sourcer of'energy through 'said coding contacts in accordance with the code rate selected fortransmission. i

5. In acoded track circuit for a railway track section, a code transmitter for applying code pulses at selected high andlow code rates tothe track rails at one end of said track section in accordance with traffic conditions comprising, asource of energy, means including said source of energy for applying code pulses at a relatively lilgh'potential to the track rails when said high code rate is selected, means including said source of energy for applying code pulses at a relatively low potential to the track rails when said low code rate is selected, and means responsive to the shunting of the track rails of said track section ior'selecting said low code rate in preference tcsaid high code'rate.

'6. A code transmitter for applying code pulses at selected high or low code rates to the track rails of a track section comprising, a source of energy, respective high and low rate coding contacts, respective high and low. resistance track resistors, circuit means for selectively connecting said source of energy across the track rails through said high rate contact and said low resistance track resistor or through said low rate contact and said high resistance track resistor, an approach control relay, and circuit means for selectively connecting said approach control relay across one or the "other of said resistors in accordance with whether said source of energy is connected to the track rails through said high :rate contact or said low rate contact.

7. The combination in a coded track circuit of a source of energy, respective high and'low rate coding contacts, respective high and low'resistance track resistors, track energization means for selectively connecting said source of energy across the track rails through said high rate contact and said low resistance track resistor or through said low rate contact and said high re sistance track'resistor, an approach control relay, circuit means for selectively connecting said approach control relay so as to be energized by the voltage drop of one or the other of said resistors selected in accordance with whether said source of energy is connected to the track rails through said high rate contact or said low rate contact, whereby said approach control relay is normally inactive but is rendered active in response to the shunting of the track rails of said track section by a train, said source to be connected to the track rails through said high rate contact as governed by traffic conditions in another track section, only provided that said approach control relay is inactive.

8. In a code transmitting organization at the exit end of a railway track section, a source of energy, circuit means including limiting resistors and coding contacts for intermittently connecting said source of energy to the track rails of said section at different selected code rates in accordance with trafiic conditions in advance, said limiting resistors having different values so that the pulses of each code rate are applied across the track rails at different appropriate potentials, an approach control relay at said exit end of said section governed by the intermittent energization of said track rails and the shunting of said track rails by a train to indicate the conditions of occupancy of said track section, and control means governed by said approach relay for acting on said circuit means 15 toselect aparticular code'ratewhen said section is occupied by a train independent of trafiic conditions in advance.

9. In a code transmitting organization at the exit end of a railway track section, a source of energy, high rate coding means including said source of energy and a limiting resistor of a particular value efiective when rendered active to apply code pulses of a relatively high potential at said high rate to the track rails of said section, low rate coding means including said source of energy and another limiting resistor of a higher value eiTective when rendered active to apply code pulses of a relatively low potential at said low rate to the track rails of said section, circuit means controlled in accordance with traffic conditions in the next section in advance for selectively rendering said high or low rate coding means active, and an approach control relay at the exit end of said section govverned by the intermittent energization of the track rails and rendered active in response to the presence of a train section for rendering said low rate coding means active and said high rate coding means inactive irrespective of the control provided by said circuit means dependent upon traffic conditions in advance, whereby code pulses of different selected rates and of appropriate potentials for such rates are applied to the track rails to operate the code receiving means at the entrance end of the section in accordance with trafiicconditions, and whereby the low rate code pulsesof low potential are applied to the track rails while a track section is occupied by a train to thereby save energy from said source and minimize the amount of current to be controlled by the said low rate coding means.

10. In a coded track circuit organization for a section of railway track in which driven code pulses are transmitted from one end of the section to receiving apparatus at the other end that is efiective to return inverse code pulses between successive driven code pulses, code apparatus at said one end comprising, a source of energy, a first means including said source of energy for applying code pulses at a relatively high potential to the track rails when said high code rate is selected, a second means including said source of energy for applying code pulses at a relatively low potential to the track-rails when said low code rate is selected, circuit means governed by trafiic conditions for the next section in advance for selecting said first or second means dependent upon the then existing trafiic condition, and means governed by said inverse code pulses and responsive to the shunting of the rails of said track section for acting on said circuit means to select said low code rate in preference to said high code rate.

11; In a coded track circuit organization for a section of railway track in which driven code pulses are transmitted from one end of the section to receiving apparatus at the other end that is efiective to return inverse code pulses between successive driven code pulses, code apparatus at said one end comprising, a source of energy, a first means including said source of energy for applying code pulses at a relatively highpotential to the track rails when said high code rateis selected, a second means including said source of energy for applying code pulses at a relatively low potential to the track rails when said low code rate is selected, circuit means governed by traflic conditions for the next section in advance for selecting said first or second means dependent upon the then existing trafi'ic condition, and inverse code receiving means at said one end of said track section responsive to the shunting oi the track rails of said track section for acting upon said circuit means to select said second means for applying code pulses at a relatively low potential and at said low code rate irrespective of the trafiic condition then existing for the track section in advance.

THOMAS J. JUDGE.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,626,643 Stolp May 3, 1927 1,662,444 Tegeler Mar. 13, 1928 2,160,640 Bossart May 30, 1939 2,275,909 Kemmerer Mar. 10, 1942 2,331,815 Thompson Oct. 12, 1943 2,362,678 Thompson Nov. 14, 1944 2,366,776 Failor Jan. 9, 1945 2,378,325 Rees June 12, 1945 

